14-inch rectangular tart pan,Heat oven to 350° F. Butter a 14-inch rectangular tart pan and set aside.,Combine the flour and baking powder in a medium bowl and set aside.,______,Heat the apricot jam and lemon juice in a small saucepan over medium-low heat, mixing until combined. Remove from heat and brush gently over the entire tart. Serve with the whipped cream, if desired.,If you don't have a rectangular tart pan, you can use a 10-inch round tart pan. The dessert can be made up to 2 days in advance, covered, and kept in the refrigerator.